The uniforms worn by the security guards are the same uniforms from Star Trek: The Motion Picture, but they're worn with the new red Starfleet uniforms, and a dark green turtleneck, which represents the security division.
There was a debate during the writing of the script as to who should be killed by the Klingons - Saavik (Robin Curtis) or David Marcus (Merritt Butrick). It was eventually decided that Marcus should die as punishment for experimenting with protomatter in the Genesis matrix.
To keep the secrecy, the name "Spock" was never used in the movie script, but instead the alias "Nacluv" (reverse of "Vulcan") was used.
The scene in which Kirk stumbles into his chair after hearing of the death of his son was an improvisation by William Shatner, who was told by Leonard Nimoy to do whatever reaction Shatner wanted to do. Shatner has never told whether he meant to miss the chair and slip to the ground, or if he had meant to simply hit the seat hard but missed going backwards.
When negotiating Kirstie Alley's contract for Star Trek II, Paramount did not offer or include any options or clauses regarding any possible sequels. According to Leonard Nimoy, this left Alley open to negotiate a new contract for Star Trek III, resulting in Alley's excessive salary demands which led her to being replaced by Robin Curtis.
Originally the scene in which Bones tries to charter a ship to Genesis generated into a bar fight. The scene didn't work so Leonard Nimoy decided to scale it back.
Studio Chief Michael Eisner resisted the idea of Leonard Nimoy directing because he mistakenly thought that the reason for Spock's death stemmed from a hatred that Nimoy had about Star Trek. This was not true, however, because Nimoy jumped at the chance to direct when the original director Nicholas Meyer turned it down.
Dame Judith Anderson was 86 years-old when she appeared in this film. She had come out of retirement after being away from films for 14 years. She was encouraged to take this part by her nephew.
Close to the end of the film, after landing on Vulcan. While Spock's body is being carried up the long staircase to begin the fal tor pan ritual, the "maidens" carrying Spock are not actually touching him. They are actually holding their hands above him, effectively levitating his body to the altar.
Marc Okrand had to update the grammar and vocabulary of the Klingon language several times when actors would get the line wrong and it was deemed easier to re-write the language than re-shoot the scene.
In a June 2009 interview, Christopher Lloyd said that the role of Klingon Commander Kruge was among one of his favorite roles he ever portrayed in his acting career.
It was Director/Star Leonard Nimoy who conceived the distinctive design of the Klingons' Bird Of Prey. At a preproduction meeting with Industrial Light And Magic, Nimoy posed his arms and hands to demonstrate the vessel's wings as they ultimately would appear in the final film. The DVD documentary, "Space Docks and Birds Of Prey", revealed that the physique of a bodybuilder in the "crab" pose, emphasizing the trapezius muscles, was also the basis for the ship's aggressive stance. Finally, the script, at the time when it was received by ILM, established that the Bird Of Prey was definitely a Romulan vessel, commandeered by Kruge. With that back story in mind, the feather-like pattern on the ship's underside was a direct tribute the original Bird Of Prey as it first appeared in the 1966 original series episode "Balance of Terror". Though the final version of Star Trek 3 (and subsequent star trek films and TV episodes) refer to the ship as purely of the Klingon fleet, the Romulan plumage-detail was never lost.
The young Spock was voiced by Frank Welker. Welker and Nimoy would go on to share the role of Megatron/Galvatron in The Transformers: The Movie. Welker would also provide numerous voices in Transformers: Revenge of the Fallen, directed by Nimoy's cousin, Michael Bay. Nimoy himself was offered the title role, but declined. He later went on to voice Sentinel Prime in Transformers: Dark of the Moon.
When Kirk calls out to Kruge, the Klingon commander has his head in his hands. According to the original storyline, Kruge is not mourning the loss of his troops, he's humiliated because Kirk was more cunning than he was. Through Kirk's apparent suicide, Kruge has been beaten and shamed.
Edward James Olmos was Leonard Nimoy's original choice for the role of Kruge. However, executive producer Harve Bennett preferred Christopher Lloyd. Nimoy finally cast Lloyd because he came off more operatic and physically intimidating.
The few Klingon phrases that Mark Lenard introduced in Star Trek: The Motion Picture was used by Marc Okrand as the basis for the Klingon language in this film. Okrand's Klingon language became a fully realized fictional language, and would be the basis for all future Klingon dialogue in future movies and television shows (as well as an obsession to become fluent in for hardcore Star Trek fans.)
The self-destruct codes for the U.S.S. Enterprise apparently haven't been changed in decades, as they are identical to those in the original series episode "Let That Be Your Last Battlefield".
Gary Faga plays the security guard who Sulu knocks out; he also played the airlock technician that Spock gave the Vulcan nerve pinch to in Star Trek: The Motion Picture.
Grace Lee Whitney, who played Janice Rand, Kirk's yeoman in season one of Star Trek and returned as transporter chief in Star Trek: The Motion Picture, makes a cameo appearance during the Enterprise's docking sequence. She is the red haired officer in the spacedock lounge who shakes her head in disapproval as she sees the ship's damage.
When McCoy enters the bar looking for transport a Tribble from the original TV Series can be seen.